I don't think anyone with psychosis is more likely to commit crime, they would just become an extremely paranoid, depressed introvert. I always found the idea that cannabis caused crime as laughable. You have to realise, cannabis effects the way you think and percieve things and if you are stoned out of your bin for 10 years and then stop smoking your brain isn't used to normality and can have serious trouble re-adjusting. Caffiene doesn't affect the way you think and percieve things it just makes you more alert and awake.